FIG. 1 shows a NPN device 100 formed by a traditional Complementary Metal Oxide Semiconductor (CMOS) process. The NPN device 100 includes a P− epitaxial layer 102 over a p-type substrate 104. The NPN device 100 further includes N+ type source and drain implants that function as an emitter, a Pbase implant that functions as a base, and a N-well that functions as a collector. The NPN device 100 is isolated by a P-well ring 106 and an optional P+ buried layer (ISOUP) 108 at the bottom of the device, as shown in FIG. 1. Typically, producing NPN devices by a traditional CMOS process is simpler and cheaper than fabricating these devices in other platforms. However, NPN devices produced by the traditional CMOS process may not provide the maximum performance of NPN devices produced in bipolar platforms. Furthermore, in CMOS platforms, an N-well is optimized for P-channel performance and a NPN collector is formed with an N-well. As such, the N-well constrains a NPN beta and breakdown voltage within an NPN device.
To improve performance, NPN devices have been constructed within a Bipolar Complementary Metal Oxide Semiconductor (BiCMOS) platform. For example, FIG. 2 shows a NPN device 200 formed by a conventional BiCMOS process. The NPN device 200 includes a N− epitaxial layer 202 over a p-type substrate 208. The NPN device 200 further includes an implanted N+ buried layer 204, an implanted P+ buried layer (ISOUP) 206, and an implanted P-well 210 that functions as an isolation ring. Typically, the implanted N+ buried layer and P+ buried layers are formed utilizing two separate masking steps to achieve selective implanting within a semiconductor substrate. Furthermore, NPN devices formed within a BiCMOS platform may use a N−epitaxial layer of proper thickness and doping concentration, to obtain a desired beta and breakdown voltage trade-off. As such, although utilizing a conventional BiCMOS platform provides a higher performing NPN device, the process also involves additional processing which leads to an increase in manufacturing costs.
Thus, what is needed is a system and method that addresses the above-identified issues. The present invention addresses such a need.